President Barack Obama has revealed Hassan Rouhani, Iran's reformist new
president had "reached out" to the US leader as the West looks to
improve ties with the isolated Tehran regime.

News that Mr Obama and Mr Rouhani had exchanged letters came after the Glasgow-educated Iranian leader declared on Twitter that he would meet William Hague, the Foreign Secretary, when the pair are in New York later this month.

Mr Obama said he believed the successful negotiations over Syria's chemical weapons should demonstrate to Iran that diplomacy can work even when military intervention is threatened.

"What they should draw from this lesson is that there is the potential of resolving these issues diplomatically," he said, adding that the pair had exchanged letters after the US leader reached out to the incoming leader.

The Foreign Office confirmed that it had set a time for talks with Mohammad Javad Zarif, the Iranian foreign minister, but said it had not been officially notified that Mr Rouhani would be there as well.

"It's a positive step and while we haven't put in a request to meet the president, we'd be happy to do so," a spokeswoman said. "Why not."

It is believed to be the first meeting between a senior British minister and an Iranian head of state in almost a decade and comes after a particularly fractious period in ties with Britain.

Britain withdrew its Tehran embassy two years ago after the security forces stood back to allow hardline mobs to ransack the compound.

Ties were suspended amid anger over sanctions and divisions over London's leading role in efforts to stop Iran's nuclear programme.

But the election of Mr Rouhani in June has prompted hopes of a more moderate approach by Iran and has seen signs that Whitehall interest in rebuilding ties.

Mr Hague tweeted earlier this month that he hoped for "meaningful talks" with Zarif on Iran's disputed nuclear programme as well as the Syrian conflict, and "reciprocal steps to improve relations".

Mr Rouhani has not confirmed his Twitter account but is an active user. It is one of two accounts followed by Mr Zarif, who has confirmed his account.

London suspended diplomatic relations with Iran after hardline demonstrators stormed its Tehran embassy in November 2011, in an attack Britain said appeared state-sponsored.

Both sides have indicated they are open to restoring ties, although the Iranians warned it would take time.

"These issues need time and negotiations on an expert level," Abbas Araqchi, the Iranian foreign ministry spokesman said. "It must be decided whether their (Britain's) approach and behaviour have changed."

Shahshank Joshi, a fellow at the Royal United Services Institute (Rusi) think tank, said it would be Britain that would need strong assurances that the new government could control its extremist elements.

"The re-establishment of ties is certainly a card that British diplomats want to play and they do see an opportunity to act as a key interlocutor as Mr Rouhani seeks to ease Iran's isolation," he said. "Trust isn't there to go back any time soon."

Britain was one of the first European countries to adopt sanctions against the Iranian central bank to put pressure on Tehran over the programme.

David Cameron told the Commons this month that there continuing concerns about Iran's behaviour.

"We have effectively reached out to the Iranian government after the recent elections. And I have written to President Rouhani, so we are prepared to start trying to have a relationship with them," Mr Cameron said.

"There is a slight holdback on our behalf because we still really have not had proper redress for the fact that they smashed up our embassy and residence.

"So we do have to enter these talks and discussions with a clear head."

Mr Obama also tentative in his conclusions yesterday about Mr Rouhani's ability to deliver change. He said he believes Mr Rouhani understands the potential for a diplomatic solution to the nuclear dispute but will not "suddenly make it easy" for the West.